Picture information reading apparatus

ABSTRACT

An information reader has a number of linear image sensors dividing one line of picture information into as many parts for reading an original. As these sensors may be relatively shifted in the subscanning direction, signal delay devices are provided corresponding to the sensors for delaying a read out signal by an amount corresponding to the respective shift of the image sensors. The invention removes severe constraints on the placement and alignment of the sensors, facilitating installation and maintenance.

BACKGROUND OF THE INVENTION

The present invention relates to a picture information reading apparatus for reading picture information by successive scanning using a plurality of linear image sensors.

In a picture image reading apparatus for reading picture information by successive scanning (raster scanning), generally, a plurality of linear image sensors (hereinafter merely referred to as image sensors) such as charge coupled devices (CCDs) are disposed in the main scanning direction of an original document, and picture signals produced by these image sensors are connected to form a single line of a serial picture signal.

FIG. 1 shows the arrangement of an optical system of such apparatus. In this apparatus, three image sensors 1₁, 1₂ and 1₃ are employed and three lenses 2₁, 2₂ and 2₃ are provided respectively corresponding to the image sensors. The picture information on an original document 3 is divided into three parts in the main scanning direction and the three image sensors 1₁ -1₃ read these three parts, respectively, correspondingly through the lenses 2₁ -2₃. In such a conventional reading apparatus, the following has been required of the optical system:

(1) The respective focuses of the lenses 2₁ -2₃ should be correctly matched to the corresponding image sensors 1₁ -1₃ ;

(2) The respective image sensors 1₁ -1₃ should be disposed at a predetermined interval in the main scanning direction so that one line of picture information can be equally divided into three parts; and

(3) The respective image sensors 1₁ -1₃ should be arranged in a straight line in the main scanning direction.

Requirement (3) requires the satisfaction of the following two particular conditions:

(i) The respective image sensors 1₁ -1₃ should be disposed in the main scanning direction; and

(ii) The respective image sensors 1₁ -1₃ should be aligned in a straight line.

Accordingly, the adjustment of the optical system has heretofore required a skilled operator and substantial time.

SUMMARY OF THE INVENTION

The present invention has been achieved in view of the above-mentioned drawbacks of the conventional apparatus, and an object of this invention is to provide a picture information reading apparatus in which the adjustment of a plurality of image sensors in the main scanning direction can be simplified.

According to the present invention, there are provided, for each of the plurality of image sensors, a pluraity of line buffers of a number of lines sufficient to correspond to the mechanical shift of the associated image sensor in the subscanning direction, so that the mechanical shift can be electrically corrected by changing the number of lines stored in the line buffers. Thus, it is not necessary to arrange the image sensors in an exact straight line, and it will suffice to merely dispose them in parallel with the main scanning direction, to thereby attain the above-mentioned object of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view showing the arrangement of an optical system in a picture information reading apparatus provided with a plurality of image sensors;

FIG. 2 is a block diagram showing a circuit configuration of the picture information reading apparatus according to the invention;

FIG. 3 is a diagram showing lines to be read by the respective image sensors; and

FIG. 4 is a time chart showing waveforms for explaining the operation of the circuit shown in FIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 2 shows the circuit configuration of a picture information reading apparatus according to a preferred embodiment of the present invention. The apparatus comprises first to third image sensors 1₁ -1₃, a timing generating circuit 6 for supplying the image sensors 1₁ -1₃ with respective start signals 5₁ -5₃ to start the transfer of picture image signals, line buffer groups 7₁₁ -7₃₃ for providing a picture signal delay, first to third data selectors 8₁ -8₃ for selecting a desired one or ones of the picture signals, and other circuit elements.

Assume now that, when the optical system of this apparatus is checked after adjustment of the optical system has been completed, it is found that the reading positions of the respective image sensors 1₁ -1₃ are relatively shifted in the subscanning direction. Further assume in particular that, as shown in FIG. 3, the line 9₁ to be read by the first image sensor 1₁ is shifted by a distance of one line (1l) from line 9₂, and that the line 9₃ to be read by the third image sensor is shifted by three lines (3l), again with line 9₂ read by the second image sensor regarded as a reference line. In this case, the operator adjusts the apparatus such that the first, the second and the third data selectors 8₁, 8₂ and 8₃ are set to select picture signals inputted to a first, a zero-th and a third input terminal D₁, D₀ and D₃, respectively.

Assume that the power supply for this apparatus is turned on after the above-mentioned adjustment has been completed. The timing generating circuit 6 produces three start signals 5₁ -5₃ at the respective timings a, c and e as shown in FIG. 4. The first start signal 5₁ is applied to the first image sensor 1₁ so as to initiate, at this timing, the transfer of one-third of a line as a first analog picture signal 11₁ (FIG. 4b). Having been transformed into a two-valued signal by a first binary transformation circuit 12₁, the first analog picture signal 11₁ is outputted as a first digital picture signal 13₁. Each of the second and third start signals 5₂ and 5₃ is generated after the lapse of a predetermined time from the first start signal, as is necessary to make the time positions of the respective image sensors 1₁ -1₃ agree in the main scanning direction. The thus generated second and third start signals 5₂ and 5₃ are applied to the second and third image sensors 1₂ and 1₃, respectively. In response to the start signals 5₂ and 5₃, the transfer of second and third analog signal 11₂ and 11₃ (FIG. 4(d), (f)) are initiated, respectively. The timings are set such that the back end portion of the first analog picture signal 11₁ and the fore end portion of the second analog picture signal 11₂ overlap on each other, and such that the back end portion of the second analog picture signal 11₂ and the fore end portion of the third analog picture signal 11₃ similarly overlap on each other, so as to prevent the original document from being discontinuously read at its divided boundary portions.

The first to third digital signals 13₁ -13₃ are respectively applied to the corresponding data selectors 8₁ -8₃ at their individual zero-th input terminals D₀ as well as to the corresponding first line buffers 7₁₁, 7₂₁ and 7₃₁ so as to be stored therein. Each of the line buffers 7₁₁, 7₂₁ and 7₃₁, similarly to the other line buffers, is constituted by a shift register for storing a corresponding one of the three picture signals respectively produced from the binary transformation circuits 12₁ -12₃. The outputs of the first line buffers 7₁₁, 7₂₁ and 7₃₁ are respectively applied to the data selectors 8₁ -8₃ at their individual first input terminals D₁ as well as to the corresponding second line buffers 7₁₂, 7₂₂ and 7₃₂. Upon the generation of the next start signals 5₁ -5₃ by the timing generating circuit 6, the second line buffers 7₁₂, 7₂₂ and 7₃₂ respectively receive data transferred from the corresponding first line buffers 7₁₁. 7₂₁ and 7₃₁ in synchronism with the corresponding start signals 5₁ -5₃. That is, the second line buffers 7₁₂, 7₂₂ and 7₃₂ are supplied with digital picture signals respectively delayed by a time corresponding one line, in comparison with the digital signals 13₁ -13₂ produced from the binary transformation circuits 12₁ -12₃.

The outputs of the second line buffers 7₁₂, 7₂₂ and 7₃₂ are respectively applied to the data selectors 8₁ -8₃ at their individual second input terminals D₂ as well as to the corresponding third line buffers 7₁₃, 7₂₃ and 7₃₃. These digital picture signals respectively applied to the third line buffers 7₁₃, 7₂₃ and 7₃₃ are delayed by a time corresponding to two lines in comparison with the corresponding digital picture signals 13₁, 13₃ produced from the binary transformation circuit 12₁ -12₅. The outputs of the third line buffers 7₁₃, 7₂₃ and 7₃₃ are respectively applied to the data selectors 8₁ -8₃ at their individual third input terminals D₃. The digital picture signals outputted from the third line buffers 7₁₃, 7₂₃ and 7₃₃ are respectively delayed by a time corresponding to three lines in comparison with the digital picture signals 13₁ -13₃.

Each of the data selectors 8₁ -8₃ is supplied with four kinds of digital picture signals, and selects only one of these digital picture signals to produce a selected digital picture signal at its output terminal OUT. The thus produced first to third digital picture signals 14₁ -14₃ are respectively applied to first to third 2-input AND circuits 15₁ -15₃ which are respectively also supplied with first to third validating signals 16₁ -16₃ generated by the timing generating circuit 6 at the timings respectively shown at FIGS. 4g-i.

The first validating signal 16₁ is produced within a period during which the first analog picture signal 11₁ is being produced so that the first AND circuit 15₁ may produce a first digital picture signal 17₁ of the same period as the first validating signal 16₁. The first digital picture signal 17₁ is delayed by a time corresponding to one line in comparison with the first digital picture signal 13₁ produced from the first binary transformation circuit 12₁.

The first digital picture signal 17₁ is turned off by the falling of the first validating signal 16₁ at a predetermined time t₁, at which time the generation of the second digital picture 14₂ is initiated. In place of the first digital picture signal 17₁, a second digital picture signal 17₂ is produced from the second AND circuit 15₂ by the second validating signal 16₂ which rises at this point of time t₁. The second digital picture signal 17₂ is delayed by a time corresponding to two lines in comparison with the second digital picture signal 13₂ produced from the second binary transformation circuit 12₂.

Similarly, the second digital picture 17₂ is switched off by the falling of the second validating signal 16₂ at a predetermined time t₂ at which time the generation of the third digital picture signal 14₃ is initiated. In place of the second digital picture signal 17₂, a third digital picture signal 17₃ is produced from the AND circuit 15₃ by the third validating signal 16₃ which rises at this point of time t₂. The third digital picture signal 17₃ is delayed by a time corresponding to three lines in comparison with the third digital picture signal 13₃ produced from the first binary transformation circuit 12₃.

The thus successively produced first to third digital picture signals 17₁ -17₃ are supplied to an OR circuit 18. The OR circuit 18 produces at its output a digital picture signal 19 which is a continuous signal of one line, and which is not shifted in the subscanning direction.

As described above, according to the present invention, it is not necessary to effect adjustment to cause the respective image sensors to perfectly align in a straight line, whereby productivity is improved and a highly accurate reading apparatus can be produced. 

What is claimed is:
 1. A picture information reading apparatus, comprising; a plurality of linear image sensors for dividing one line of picture information into parts in a main scanning direction, so as to respectively read said one line of picture information in said parts, and picture signal delaying means provided respectively corresponding to said plurality of linear image sensors, for correcting a subscanning direction shift in reading positions between said image sensors by delaying picture signals by an amount corresponding to said shift, whereby the picture signal produced from each of said linear image sensors is corrected by said picture signal delaying means so that corrected picture signals are successively read, wherein each said picture signal delaying means comprises a data selector and a plurality of serially connected shift registers, an output of each said register being applied to said data selector.
 2. An apparatus as claimed in claim 1, said picture signals being applied directly to said data selectors, bypassing said shift registers.
 3. An apparatus as claimed in claim 1, further including timing generator means for outputting validating signals, and gate means receiving said validating signals as well as output signals from said data selector means. 